import math
import sys
def inp():
    return int(raw_input())
def linp():
    return map(int, raw_input().split())
q=inp()
for _ in xrange(q):
    n=inp()
    li=[]
    for i in xrange(n):
        a, b = linp()
        li.append([a, b])
    Y = sorted(li, key=lambda x:(x[0]))
    X = sorted(li, key=lambda x:(x[1]))
    #print Y, X
    c = X[0][1]
    d = X[n-1][1]
    a=Y[0][0]
    b=Y[n-1][0]
    flag=0
    for i in li:
        if (i[0]==a or i[0]==b) or (i[1]==c or i[1]==d): continue
        flag=1
        break
    print "YES" if flag==0 else "NO"